L.A. Wilts as Temperatures Soar; Forecast Calls for More of Same : Weather: The heat is expected to last at least through Tuesday. Three swimmers apparently drown.

A high-pressure system that stalled over Southern California drove inland temperatures into the low 100s Sunday and made most other areas nearly as miserable, but not enough to set records.

At Castaic Lake, two people apparently drowned in separate accidents, sheriff’s deputies said. Sandra Delion, 13, of Los Angeles, was pronounced dead at Henry Mayo Newhall Memorial Hospital in Valencia at 12:54 p.m. She had been swimming with friends when she disappeared in about five feet of water, officers said.

Shortly before 5 p.m. an unidentified man, who reportedly had drunk several beers with a friend, jumped from a rented rowboat to cool off and apparently drowned, deputies said. But searchers failed to recover the man’s body.

Along the coast, riptides combined with moderate beach crowds to keep lifeguards busy. An unidentified woman drowned at Dockweiler State Beach while taking a pre-dawn swim alone.

The afternoon high of 99 at the Los Angeles Civic Center was three degrees short of the record 102 set in 1956, said Steve Burback, meteorologist for WeatherData Inc., which provides forecasts for The Times.

Burback said there was nothing particularly unusual about the heat wave. The humidity, which has been high at times during the summer, was a relatively low 21%.

“The only place where it will be nice will be at the beaches,” Burback said, adding that there is no relief in sight, at least until after Tuesday. “It’s just plain hot.”

For Los Angeles Dodgers catcher Rick Dempsey, behind the plate for the entire nine innings in Sunday’s 6-4 victory over Cincinnati, it wasn’t just hot, “it was ugly.”

Dempsey said it probably was the hottest game he has caught and he has played in parts of four decades. And there was no way to cool off.

“You just get down and sweat,” he said.

Stadium organist Nancy Hefley did her best to help the sweltering crowd, playing “Let It Snow, Let It Snow, Let It Snow.”

An estimated 675,000 people trekked to county beaches to escape the heat, said county lifeguard Capt. Robert Buchanan.

“It’s a good, solid crowd but it’s not a maximum,” he said.

Two-to-four foot surf and riptides on southwest facing beaches resulted in about 150 rescues, Buchanan said.

“You start making over 100 rescues a day and you’re pretty active.”

At the Los Angeles County Fair in Pomona, no serious health problems were reported by fair-goers, possibly because air conditioning was installed in exhibit halls last year, said spokesman Sid Robinson.

“It was 105 at 3 o’clock,” Robinson reported. “People are finding cool places. Nobody’s jumping in the ponds, but they’re staying cool as best they can.”

Other high temperatures in the area Sunday included 108 at Ontario, 102 in Northridge and 100 in Newhall, according to WeatherData.